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  • 1.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Impact of Secondary Interactions in Asymmetric Catalysis2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions.

    The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained employing hydroxy- and methoxy-containing ligands in the catalytic reaction. This type of hydrogen bond was further studied in phenanthroline metal complexes. As expected for a hydrogen bond, the strength of the bond was found to increase with increased electron density at the metal and with increased acidity of the hydroxy protons.

    The second part deals with the use of hydroxy- and methoxy-containing phosphinooxazoline ligands in the rhodium- and iridium-catalyzed asymmetric hydrosilylation reaction. The enantioselectivities obtained were profoundly enhanced upon the addition of silver salts. This phenomenon was explained by an oxygen–metal coordination in the catalytic complexes, which was confirmed by NMR studies of an iridium complex. Interestingly, the rhodium and iridium catalysts nearly serve as pseudo-enantiomers giving products with different absolute configurations.

    The final part deals with ditopic pyridinobisoxazoline ligands and the application of their metal complexes in asymmetric cyanation reactions. Upon complexation, these ligands provide catalysts with both Lewis acidic and Lewis basic sites, capable of activating both the substrate and the cyanation reagent. Lanthanide and aluminum complexes of these ligands were found to catalyze the addition of the fairly unreactive cyanation reagents ethyl cyanoformate and acetyl cyanide to benzaldehyde, whereas complexes of ligands lacking the Lewis basic coordination sites failed to do so.

  • 2.
    Frölander, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Csöregh, Ingeborg
    KTH.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    OH–Pd Hydrogen Bonding in Pd(0)–Olefin Complexes Containing Hydroxy-Substituted LigandsManuscript (Other academic)
  • 3.
    Frölander, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lutsenko, Serghey
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Conformational preferences and enantiodiscrimination of phosphino-4-(1-hydroxyalkyl)oxazoline-metal-olefin complexes resulting from an OH-metal hydrogen bond2005In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 70, no 24, p. 9882-9891Article in journal (Refereed)
    Abstract [en]

    Phosphinooxazolines carrying (1-hydroxy-1-phenyl)methyl and (1-methoxy-1-phenyl)methyl substituents in the 4 position of the oxazoline ring exhibit contrasting behavior in Pd-and Ir-catalyzed allylic alkylations. Whereas catalysts with the methoxy-containing ligand generally provide products with high ee's, use of catalysts prepared from the hydroxy-containing ligand results in products with low ee's or even racemates. DFT calculations suggest the presence of a hydrogen bond with Pd(0) as the proton acceptor in the hydroxy-containing olefin-Pd(0) complexes, which induces a conformational change in the ligand, leading to different stereoselectivity.

  • 4.
    Frölander, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lutsenko, Serghey
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    OH-Metal hydrogen bond in Pd- and Ir-catalyzed allylic alkylations2006In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, 2006, p. ORGN-259-Conference paper (Other academic)
    Abstract [en]

    Phosphinooxazolines carrying 4-hydroxybenzyl and 4-methoxybenzyl substituents exhibit contrasting behavior in Pd- and Ir-catalyzed allylic alkylations.  Whereas catalysts with the methoxy-contg. ligand generally provide products with high ee's, use of catalysts prepd. from the hydroxy contg. ligand results in products with low ee's or even racemates.  DFT calcns. suggest the presence of a hydrogen bond with Pd(0) as proton acceptor in the hydroxy contg. olefin Pd(0) complexes, which induces a conformational change in the ligand leading to different stereoselectivity.  We have previously obsd. the same kind of dramatic changes of enantioselectivities in palladium-catalyzed allylations upon methylation of hydroxy-contg. pyridinooxazolines and bisoxazolines.

  • 5.
    Frölander, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ag+-Assisted Hydrosilylation: Complementary Behavior of Rh and Ir Catalysts (Reversal of Enantioselectivity)2007In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 9, no 7, p. 1371-1374Article in journal (Refereed)
    Abstract [en]

    The presence of a suitably situated hydroxy function in a PHOX ligand leads to an enhancement of the enantioselectivity in Rh-catalyzed hydrosilylations of prochiral ketones in the presence of AgBF4 (95% ee for acetophenone as compared to 75% using i-Pr-phosphinooxazoline (PHOX)). Exchanging Rh for Ir affords the product with the opposite absolute configuration (78% ee).

  • 6.
    Frölander, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Tilliet, Mélanie
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Lundgren, Stina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Levacher, Vincent
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Bifunctional Pybox Ligands: Application in Cyanations of BenzaldehydeManuscript (Other academic)
  • 7.
    Hallman, Kristina
    et al.
    KTH, Superseded Departments, Chemistry.
    Frölander, Anders
    KTH, Superseded Departments, Chemistry.
    Wondimagegn, Tebikie
    KTH, Superseded Departments, Chemistry.
    Svensson, Mats
    KTH, Superseded Departments, Chemistry.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    OH–Pd(0) Interaction as a Stabilizing Factor in Palladium-Catalyzed Allylic Alkylations2004In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 101, no 15, p. 5400-5404Article in journal (Refereed)
    Abstract [en]

    In palladium-catalyzed alkylations of allylic acetates with malonate as nucleophile, catalysts with oxazoline ligands bearing hydroxymethyl substituents in 4-position have been shown by density functional theory computations to undergo a conformational change on nucleophilic attack, which is accompanied by reduction of Pd(II) to Pd(0). The conformations of the Pd(0) complexes were shown to be governed by the presence of a hydrogen bond with the metal center acting as a hydrogen bond acceptor. The conformational change, which is absent in catalysts with O-alkylated analogs, largely affects the enantioselectivity of the catalytic process. This process is a previously uninvestigated example of where this type of weak hydrogen bond has been shown to influence the stereochemistry of a chemical reaction.

  • 8.
    Moberg, Christina
    et al.
    KTH, Superseded Departments, Chemistry.
    Belda, O.
    Frölander, Anders
    KTH, Superseded Departments, Chemistry.
    Lundgren, S.
    Zalubovskis, Raivis
    KTH, Superseded Departments, Chemistry.
    Enantio- and regioselectivity in Palladium- and Molybdenum-Catalyzed Allylic Alkylations2004In: Latvian Journal of Chemistry, ISSN 0868-8249, p. 131-138Article in journal (Refereed)
  • 9.
    Moberg, Christina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    ORGN 31-Secondary interaction in hydroxy-containing phosphinooxazolines2007In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 234, p. 31-ORGN-Article in journal (Other academic)
    Abstract [en]

    Phosphinooxazolines, first employed by Williams, Pfaltz, and Helmchen, serve as versatile ligands for a variety of asym. catalytic reactions.  The hydroxy group in hydroxy-contg. phosphinooxazolines such as 1 can take part in hydrogen bonding to low valent metal ions, thereby affecting the conformation and, as a result, the stereochem. of catalytic reactions.  The hydroxy group is also capable of coordinating to high valent metal ions via the oxygen atom, resulting in more rigid complexes.  This leads for example to enhanced enantioselectivity in Rh- and Ir-catalyzed hydrosilylations of prochiral ketones.  The influence of these secondary interaction on the conformation and dynamics of metal complexes and on the selectivity in catalytic reactions will be discussed.

  • 10.
    Tilliet, Mélanie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Levacher, Vincent
    UMR 6014 IRCOF, CNRS, Université et INSA de Rouen.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Convenient Preparation of Bifunctional Pybox Ligands2008In: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 64, no 44, p. 10244-10249Article in journal (Refereed)
    Abstract [en]

     Starting from a common easily available pybox derivative, chiral ditopic ligands with pendant Lewis basic sites consisting of amine or phosphine oxide functions attached in the 4-positions of the oxazoline rings were prepared by simple synthetic procedures. From the same pybox derivative, a macrocyclic ligand containing a diaza-18-crown-6-ether ring linked via triazole groups was obtained employing 'click' chemistry.

  • 11.
    Tilliet, Mélanie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lundgren, Stina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Levacher, Vincent
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Evaluation of new pyridine-bis(oxazoline) ligands in asymmetric catalysisManuscript (Other academic)
  • 12.
    Tilliet, Mélanie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Frölander, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zetterberg, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Szabo, Zoltan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Influence of Ligand Secondary Interactions on Dynamic Processes in Alkene Ir ComplexesManuscript (Other academic)
1 - 12 of 12
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